In fabricating a dental bridge, it is common for a dentist to prepare teeth that are to receive the bridge by grinding the teeth to a generally upwardly tapered shape. A impression of the prepared teeth is then made by the dentist and typically sent to a dental technician for fabrication of a bridge to fit the prepared teeth. The technician usually fills the impression with gypsum to form a plaster cast of the patient's teeth and a set of parallel tapered metal dowel pins is then secured in the bottom of the cast with a pin underlying each prepared tooth. The cast is then mounted atop a wet plaster base with the parallel pins extending through the base. When the base dries, the bottom of the base is buffed or sanded so that the pin ends are flush with the base bottom. The cast is then cut into segments called working dies with a small saw with each segment or die bearing a cast of a prepared tooth. The working dies can thus be individually removed from the base by pressing their corresponding dowel pins upwardly from the bottom of the base. The segmented cast mounted to the base is then usually covered with wax to form a pattern wax coping pattern of the teeth. When this wax pattern dries, the segmented waxed cast can be separated from the base by pressing the tapered dowel pins upwardly from the bottom of the base whereupon the individual working dies can be removed from the wax with the resulting, wax pattern being used to cast the bridge or crown.
Heretofore, the tapered dowel pins have been pressed from the base by hand to separate the waxed cast from the base. Many times, the pins are not dislodged from the holes in the base simultaneously causing some of the working dies to separate from the base before others and consequently resulting in distortion or warping of the wax pattern. A bridge cast from such a distorted pattern also bears the distortion such that it might not fit the patient's teeth. In this event, a new bridge often must be fabricated from scratch. Since it is difficult to determine that a pattern has been warped until the finished bridge is completed, many hours of tedious work molding the bridge from the warped impression is sometimes sacrificed.
A long felt and unaddressed need exists, therefore, for a method and apparatus for simultaneously separating the waxed dies of a dental cast from their plaster base such that the resulting wax pattern does not become warped or distorted. It is to the provision of such a method and apparatus that the present invention is primarily directed.